My femra can't have shellfish.
Oysters and mussels are common shellfish and are eaten by a lot of people.
But a lot of people forget that snails, scallops, squid, and even octopus count as shellfish.
My femra can get very sick if she eats any of these and might even need to go to the hospital.
Even being in the same house when someone is cooking shellfish can cause a reaction, so please be considerate.